US20040261712A1 - Plasma processing apparatus - Google Patents

Abstract

In a plasma processing apparatus that executes plasma processing on a semiconductor wafer placed inside a processing chamber by generating plasma with a processing gas supplied through a gas supply hole at an upper electrode (shower head) disposed inside the processing chamber, an interchangeable insert member is inserted at a gas passing hole at a gas supply unit to prevent entry of charged particles in the plasma generated in the processing chamber into the gas supply unit. This structure makes it possible to fully prevent the entry of charged particles in the plasma generated inside the processing chamber into the gas supply unit.

Description

BACKGROUND OF THE INVENTION
• 1. Field of the Invention[0001]
• The present invention relates to a plasma processing apparatus, and more specifically, it relates to a plasma processing apparatus that does not allow charged particles of plasma generated in a processing chamber to enter a gas supply unit.[0002]
• 2. Description of the Related Art[0003]
• Plaza processing apparatuses in the known art include those that execute plasma processing such as etching on the work surface of a workpiece, e.g., a semiconductor wafer (hereafter simply referred to as a “wafer”) placed within a processing chamber by, for instance, supplying a processing gas from a gas supply unit into the processing chamber and generating plasma with the processing gas.[0004]
• The gas supply unit in such a plasma processing apparatus is constituted as a shower head having numerous gas supply holes through which the processing gas is supplied into the processing chamber. The plasma processing apparatus may be, for instance, a plane parallel plasma processing apparatus having a lower electrode disposed within the processing chamber, on which the workpiece is placed. The gas supply unit is constituted of a shower head also functioning as an upper electrode which is disposed at the ceiling of the processing chamber so as to face opposite the lower electrode.[0005]
• The gas supply unit includes an electrode plate that constitutes the lower surface thereof, in which numerous gas supply holes are formed and an electrode support body supporting the electrode plate. Inside the electrode support body, a buffer chamber is formed as a space located above the electrode plate and communicating with a gas supply pipe, and the buffer chamber also communicates with the gas supply holes at the electrode plate. The gas flowing in through the gas supply pipe is first supplied into the buffer chamber and is then guided from the buffer chamber into the processing chamber via the gas supply holes at the electrode plate.[0006]
• However, charged particles such as electrons and ions in the plasma generated with the processing gases inside the processing chamber may enter the buffer chamber through the gas supply holes at the gas supply unit in the plasma processing apparatus. If charged particles in the plasma enter the gas supply unit (shower head), a glow discharge occurs in the buffer chamber at the gas supply unit, giving rise to problems such as reaction products becoming adhered to the inner surfaces of the gas supply unit and the inner surfaces of the gas supply unit becoming corroded.[0007]
• These problems are addressed in, for instance, Japanese Patent Laid-open Publication No. 9-275093, which discloses a structure achieved by mounting a screw having a hole decentered from the central axis at each gas outlet hole of the gas supply means so that there is no clear passage from one opening end of the gas supply hole through the other opening end to prevent entry of electrons and ions in the plasma into the gas supply means. This technology was developed in order to minimize the entry of charged particles through the mean free path based upon the concept that the charged particles in the plasma are allowed to enter the gas supply means since the thickness of the electrode plate (the height of the gas supply holes) is approximately equal to the length of the mean free path of the charged particles in the plasma.[0008]
• However, the charged particles in the plasma enter the gas supply means not only through the mean free path but also because of other factors. For instance, the potential (the ground potential) at the electrode support body constituting the upper wall of the buffer chamber in the gas supply unit may become lower than the potential (ground potential) at the electrode plate constituting the lower wall of the buffer chamber. In such an event, the charged particles in the plasma are allowed to readily enter the buffer chamber from the gas supply holes at the electrode plate toward the electrode support body. In addition, while the gas supply unit normally maintains a field free state inside, the equipotential line will become skewed at an end of a gas supply hole and shifts into the gas supply hole if the gas supply hole is clear, thereby allowing a concentration of energy of the electrons and the like and allowing the electrons and the like to readily enter the gas supply hole.[0009]
• For this reason, charged particles in the plasma cannot be fully prevented from entering the gas supply means simply by mounting a screw having a hole decentered from the central axis at each gas outlet hole of the gas supply means as disclosed in Japanese Patent Laid-open Publication No. 9-275093. For instance, since high-frequency power causes charged particles such as electrons to vibrate along a direction perpendicular to the equipotential line, the oscillating direction of the charged particles becomes tilted if the equipotential line becomes skewed and shifts into the end portion of the gas supply hole. In such a case, the entry of the charged particles cannot be fully prevented simply by mounting a screw having a hole decentered from the central axis.[0010]
• Furthermore, entry of the charged particles in the plasma is most likely to occur when various conditions such as a specific gas supply hole diameter, a specific gas type and a specific plasma density coincide. This leads to a concept that if the gas passage at the gas supply hole can be altered in correspondence to predetermined conditions, the entry of the charged particles in the plasma into the gas supply unit can be prevented more effectively.[0011]
• Accordingly, an object of the present invention, which has been completed by addressing the problems discussed above, is to provide a plasma processing apparatus capable of fully preventing charged particles in the plaza generated inside the processing chamber from entering the gas supply unit.[0012]
SUMMARY OF THE INVENTION
• In order to achieve the object described above, in an aspect of the present invention, a plasma processing apparatus that executes plasma processing on a workpiece placed inside a processing chamber by generating plasma with a processing gas supplied through gas supply holes of gas supply unit disposed inside the processing chamber, characterized in that an interchangeable insert member, which prevents charged particles in the plasma generated inside the processing chamber from entering the gas supply unit, is mounted at each gas supply hole at the gas supply unit, is provided.[0013]
• The insert member may include a gas passage communicating between the entry side and the exit side of the gas supply hole, and the gas passage may include a passage which extends along a direction perpendicular to or at an angle to a central axis of the gas supply hole so as to regulate the flow along the central axis.[0014]
• Alternately, the insert member may include a gas passage formed, for instance, as a spiral gas passage, which communicates between the entry side and the exit side of the gas supply hole while constantly regulating the flow in the gas supply hole along the central axis. Such a gas passage may be formed so that its section has a width (groove depth) along the direction perpendicular to the central axis of the gas supply hole larger than the thickness of the passage along the central axis of the gas supply hole.[0015]
• In addition, an insert member constituted of a specific material may be used in conjunction with a specific gas type used for the plasma processing. Furthermore, the shape of the gas passage in the insert member may be determined in correspondence to the density of the plasma generated in the processing chamber.[0016]
• Even if charged particles such as electrons in the plasma enter through the gas supply hole the flow of the charged particles inside the gas supply hole is regulated along the central axis and the charged particles are thus caused to collide into the inner wall or the like of the insert member and lose energy before they reach the upper end of the insert member in the plasma processing apparatus according to the present invention described above. In particular, even if the equipotential line becomes skewed at the end of the gas supply hole, the oscillating direction of the charged particles such as electrons becomes tilted and, as a result, the charged particles enter the gas supply hole, the movement of the charged particles along the central axis is regulated through the gas passage. Thus, the entry of the charged particles in the plasma into the gas supply unit can be prevented with a high degree of reliability. This, in turn, effectively prevents any occurrence of a glow discharge in the gas supply unit since no energy is transferred into the gas supply unit.[0017]
• Moreover, since interchangeable insert members are used according to the present invention, optimal insert members can be mounted at the gas supply unit in correspondence to various conditions such as the specific gas type and the specific plasma density.[0018]
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a schematic sectional view of the structure adopted in an etching apparatus in an embodiment of the present invention;[0019]
• FIG. 2 is a schematic sectional view of the structure adopted in the upper electrode (shower head) in the embodiment;[0020]
• FIG. 3 is a schematic a sectional view of the upper electrode which does not include the insert members achieved in the embodiment;[0021]
• FIG. 4 presents a structural example that may be adopted in the insert members in the embodiment, with FIG. 4A showing an external view of an insert member and FIG. 4B showing a sectional view of an insert member;[0022]
• FIG. 5 presents another structural example that may be adopted in the insert members in the embodiment, with FIG. 5A showing an external view of an insert member and FIG. 5B showing a sectional view of an insert member;[0023]
• FIG. 6 is a perspective of another structural example that may be adopted in the insert members in the embodiment;[0024]
• FIG. 7 presents sectional views of the insert member in FIG. 6, with FIG. 7A showing a sectional view of the insert member in FIG. 6 taken along A-A and FIG. 7B showing a sectional view of the insert member in FIG. 6 taken along B-B;[0025]
• FIG. 8 schematically illustrates the overall structure of another plasma processing apparatus in which the present invention may be adopted;[0026]
• FIG. 9 schematically illustrates the structure of an essential portion of the plasma processing apparatus in FIG. 8;[0027]
• FIG. 10 schematically illustrates the structure of an essential portion of the plasma processing apparatus in FIG. 8;[0028]
• FIG. 11 schematically illustrates the structure of an essential portion of the plasma processing apparatus in FIG. 8;[0029]
• FIG. 12 is a schematic sectional view of the structure adopted in another plasma processing apparatus in which the present invention may be adopted;[0030]
• FIG. 13 is a sectional view of the plasma processing apparatus in the embodiment shown in FIG. 12 with its upper electrode set at a processing position;[0031]
• FIG. 14 presents simplified views of the upper electrode unit achieved in the embodiment, with FIG. 14A showing the upper electrode unit with the upper electrode set at a retracted position and[0032]
• FIG. 14B showing the upper electrode unit with the upper electrode set at the processing position;[0033]
• FIG. 15 shows the structure adopted in the means for drive control at the upper electrode drive mechanism in the embodiment;[0034]
• FIG. 16 is a block diagram of the upper electrode position control executed by the CPU shown in FIG. 15;[0035]
• FIG. 17 shows the structure adopted in the pneumatic circuit in the embodiment;[0036]
• FIG. 18 illustrates the functions of the pneumatic circuit in the embodiment;[0037]
• FIG. 19 illustrates the functions of the pneumatic circuit in the embodiment;[0038]
• FIG. 20 shows the results of position control achieved by driving the upper electrode in the embodiment upward; and[0039]
• FIG. 21 shows the results of position control achieved by driving the upper electrode in the embodiment downward.[0040]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
• The following is a detailed explanation of the preferred embodiments of the present invention, given in reference to the attached drawings. It is to be noted that the same reference numerals are assigned to components having substantially identical functions and structural features in the specification and drawings to preclude the necessity for a repeated explanation thereof.[0041]
• (Plasma Processing Apparatus Achieved in an Embodiment of the Present Invention)[0042]
• The structure adopted in the plasma processing apparatus achieved in an embodiment of the present invention is now explained in reference to FIG. 1. FIG. 1 is a sectional view of the structure of a plasma processing apparatus achieved in the embodiment. A[0043]plasma processing apparatus100, which is an RIE plasma etching apparatus, includes a cylindrical processing chamber (chamber)110 constituted of a metal such as aluminum or stainless steel. Theprocessing chamber110 is grounded for protection.
• Inside the[0044]processing chamber110, a disk-shaped lower electrode (susceptor)112, on which a workpiece such as a semiconductor wafer (hereafter simply referred to as a wafer) is placed, is disposed. Thelower electrode112 constituted of, for instance, aluminum is supported by a barrel-shaped supportingunit116 extending upward perpendicular to the bottom of theprocessing chamber110 via an insulating barrel-shapedholding unit114. At the upper surface of the barrel-shapedholding unit114, a focus ring118 constituted of, for instance, quartz, which encircles the upper surface of thelower electrode112, is disposed.
• An evacuating[0045]passage120 is formed between the side wall of theprocessing chamber110 and the barrel-shaped supportingunit116. Anannular baffle plate122 is mounted either at the entrance to or in the middle of the evacuatingpassage120, and anevacuation port124 is provided at the bottom of the evacuatingpassage120. Anevacuation device128 is connected to theevacuation port124 via anevacuation pipe126. Theevacuation device128, which includes a vacuum pump (not shown), is capable of reducing the pressure in the processing space within theprocessing chamber110 to a predetermined degree of vacuum. Agate valve130, which opens/closes the delivery bay through which the wafer W is carried in/out is mounted at the side wall of theprocessing chamber110.
• A high-frequency source[0046]132 for plasma generation and also for RIE is electrically connected to thelower electrode112 via amatcher134 and apower supply rod136. High-frequency power with a predetermined frequency, e.g., 60 MHz, is applied to thelower electrode112 from the high-frequency source132. In addition, at the ceiling of theprocessing chamber110, a shower head (hereafter referred an “upper electrode”)138 to be detailed later, which is used to supply a processing gas and also functions as an upper electrode, is disposed at a position facing opposite thelower electrode112. The potential at theupper electrode138 is set to ground level. Thus, the high-frequency voltage from the high-frequency source132 is capacitatively applied between thelower electrode112 and theupper electrode138.
• An electrostatic chuck[0047]140 that holds the wafer W by electrostatically attracting the wafer W is provided at the upper surface of thelower electrode112. The electrostatic chuck140 is constituted by enclosing an electrode140aformed from a conductive film between a pair of insulatingfilms140band140c. ADC source142 is electrically connected with the electrode140avia aswitch143. As a DC voltage is supplied from theDC source142, the wafer W is attracted and held onto the electrostatic chuck140 with the resulting coulomb force.
• A[0048]coolant chamber144, which may extend along, for instance, the circumferential direction is provided inside thelower electrode112. A coolant such as cooling water sustaining a predetermined temperature and supplied from achiller unit146 viapipings148 and150 circulates through thecoolant chamber144. The temperature of the wafer W on thelower electrode112 can be controlled in correspondence to the temperature of the coolant. In addition, a heat transfer gas such as an He gas is supplied from a heat transfergas supply unit152 via agas supply line154 to the space between the upper surface of the electrostatic chuck140 and the back surface of the wafer W.
• As FIG. 2 also shows, the upper electrode (shower head)[0049]138 includes anelectrode plate156 located on the lower side, at which numerousgas passing holes156aare formed, anelectrode support body158 which detachably supports theelectrode plate156 and anintermediate member157 disposed on top of theelectrode plate156 and havinggas communicating holes157aeach communicating with one of thegas passing holes156aat theelectrode plate156. The gas supply holes at the gas supply unit according to the present invention are each constituted with agas passing hole156aand the correspondinggas communicating hole157adescribed above. Inside theelectrode support body158, abuffer chamber160 is formed and agas supply piping164 extending from a processinggas supply unit162 is connected to agas supply port160aat thebuffer chamber160.
• The[0050]processing chamber110 is enclosed by adipole ring magnet166. Thedipole ring magnet166 is constituted with a pair of annular or coaxial magnets disposed at an upper position and a lower position over a distance from each other in the embodiment. The magnets constituting thedipole ring magnet166 are each achieved by housing a plurality of anisotropic segment pole magnets in a ring-shaped casing formed of a magnetic material so that they form uniform horizontal magnetic fields that are oriented in a single direction as a whole inside theprocessing chamber110. As the processing gas is supplied into theprocessing chamber110, a magnetron discharge is caused by an RF electric field along the vertical direction attributable to the high-frequency source132 and the horizontal magnetic field attributable to thedipole ring magnet166 in the space between theupper electrode138 and thelower electrode112 in theprocessing chamber110 and, as a result, high-density plasma is generated near the surface of thelower electrode112.
• The plasma processing apparatus includes a[0051]control unit168 that controls the individual units in the apparatus. Thecontrol unit168 controls the operations of, for instance, theevacuation device128, the high-frequency source132, theswitch143 for the electrostatic chuck, thechiller unit146, the heat transfergas supply unit152 and the processinggas supply unit162. Thecontrol unit168 may be connected to a host computer within the factory (not shown) to enable control from the host computer.
• When executing, for instance, an etching process with the[0052]plasma processing apparatus100 structured as described above, thegate valve130 is first set in an open state to allow the wafer W, i.e., the workpiece, to be carried into theprocessing chamber110 and placed on thelower electrode112. At this time, a DC voltage from theDC source142 is applied to the electrode140aof the electrostatic chuck140 to electrostatically attract the wafer W onto thelower electrode112. Then, a specific type of processing gas such as NH3 is supplied from the processinggas supply unit162 into theprocessing chamber110 at a predetermined flow rate and a predetermined flow rate ratio, and the pressure inside theprocessing chamber110 is set to a predetermined value via theevacuation device128. In addition, high-frequency power at a specific frequency is applied from the high-frequency source132 to thelower electrode112 at a predetermined power level. The processing gas supplied into theprocessing chamber110 via theupper electrode138 as described above is raised to plasma between the twoelectrodes112 and138 through a high-frequency discharge and the work surface of the wafer W is etched with radicals and ions occurring in the plasma.
• By applying high-frequency power at a frequency higher than that in the related art, e.g., 50 MHz or higher, to the[0053]lower electrode112, a higher density can be achieved for the plasma in a more desirable state of dissociation and high density plasma can be formed at a lower pressure.
• Next, the upper electrode (shower head)[0054]138 representing an example that may be adopted in the gas supply unit in the embodiment is explained in further detail in reference to drawings. FIG. 2 is a sectional view of the structure adopted in the upper electrode in the embodiment, whereas FIG. 3 presents another example of an upper electrode provided for comparison with the upper electrode in the embodiment.
• As shown in FIG. 2, insert[0055]members200 are inserted atgas passing holes156aconstituting part of the gas supply holes, which are located at theelectrode plate156 in theupper electrode138 in the embodiment. Theinsert members200, which can be attached to and detached from theelectrode plate156 freely, can be replaced byinsert members200 with any of various structures featuring gas passages formed in different shapes and constituted of different materials, in correspondence to various conditions such as the gas type and the plasma density level. Theinsert members200 are used to prevent charged particles such as electrons and ions in the plasma generated within theprocessing chamber110 from entering the upper electrode through thegas passing holes156a. Theinsert members200 each include agas passage212 through which the processing gas flows. Thegas passage212 is formed so that entry of charged particles in the plasma is disallowed while the processing gas is allowed to flow through it. It is to be noted that the structure of theinsert members200 is to be described in detail later.
• If the[0056]insert members200 are not inserted at thegas passing holes156aof theupper electrode138 as shown in FIG. 3, charged particles in the plasma may enter theupper electrode138 through thegas passing holes156aat theelectrode plate156. Electrons, which move particularly fast among charged particles, can enter the gas supply unit with ease. If charged particles in the plasma enter theupper electrode138, a glow discharge occurs in thebuffer chamber160 inside theupper electrode138, which results in reaction products becoming adhered to the inner surfaces at theupper electrode138 and corrosion inside the upper electrode.
• In addition, while the charged particles in the plasma are allowed to enter the[0057]upper electrode138 when the length of the mean free path of the charged particles in the plasma is substantially equal to or greater than the thickness of the electrode plate156 (the height of the gas supply holes), entry of charged particles may be attributed to the following causes as well. For instance, the potential (the ground potential) at theelectrode support body158 constituting the upper wall of thebuffer chamber160 in theupper electrode138 may become lower than the potential (the ground potential) at theelectrode plate156, which is in electrical contact with theintermediate member157 constituting a lower wall of thebuffer chamber160. In such an event, charged particles in the plasma are allowed to enter thebuffer chamber160 with greater ease from thegas passing holes156aat theelectrode plate156 and flow toward theelectrode support body158.
• In addition, while the[0058]upper electrode138 normally maintains a field free state inside, the equipotential line will become skewed at the ends of the gas supply holes (each constituted with agas passing hole156aand the correspondinggas communicating hole157a) and shifts into any clear gas supply hole, thereby allowing a concentration of the energy of the electrons and the like in the gas supply hole. Namely, when charged particles such as electrons are caused to oscillate by high-frequency power, they oscillate along a direction perpendicular to the equipotential line and thus, if the equipotential line becomes skewed and shifts into the end of a gas supply hole, the oscillating direction of the charged particles, too, becomes tilted, which causes the energy of the charged particles such as electrons to readily concentrate at the end portion of the gas supply hole. As a result, the charged particles such as electrons are allowed to enter the gas supply holes with ease. Under these circumstances, the charged particles are more likely to enter thebuffer chamber160 while holding a high level of energy.
• Such entry of charged particles from the plasma can be prevented by forming a passage extending along a direction perpendicular to or at an angle to the central axis of each gas supply hole so as to regulate the flow along the central axis. The entry of the charged particles in the plasma can be prevented more effectively as the length of the passage extending along the direction perpendicular to or at an angle to the central axis increases, since the charged particles in the plasma along the vertical direction will more readily collide with the wall or the like defining the gas passage as the length of the passage extending along the direction perpendicular to or at an angle to the central axis increases and thus, the energy level of the charged particles in the plasma can be kept low. The presence of such a passage at each gas supply hole prevents the charged particles in the plasma from advancing to the[0059]buffer chamber160 at theupper electrode138.
• Furthermore, the charged particles in the plasma are likely to enter the[0060]upper electrode138 most readily when various conditions such as a specific gas supply hole diameter, a specific gas type and a specifics plasma density level coincide. This leads to a concept that if the gas passage at the gas supply hole can be altered in correspondence to predetermined conditions, the entry of the charged particles from the plasma into theupper electrode138 can be prevented more effectively.
• Based upon this concept, an[0061]insert member200 is inserted at each of the gas supply holes at theupper electrode138 and the part of the gas passage formed at the insert member, which extends vertically or at an angle is made to range over a sufficient length, according to the present invention. In addition,insert members200 can be replaced with a different type of insert members in conformance to various conditions such as the gas type and the plasma density so as to alter the passage through the gas supply hole to adjust to specific conditions.
• Next, structural examples that may be adopted in the[0062]insert members200 inserted at thegas passing holes156aconstituting part of the gas supply holes at theupper electrode138 as described above are explained in reference to drawings. FIG. 4 presents a structural example that may be adopted in the insert members mounted at the gas supply holes of the upper electrode. FIG. 4A presents an external view of an insert member, whereas FIG. 4B presents a sectional view of the insert member mounted at agas passing hole156a.
• As shown in FIGS. 2 and 4B, the[0063]gas passing holes156aformed at theelectrode plate156 of theupper electrode138 are each constituted with ahole156bformed on the side toward theintermediate member157 and ahole156cwhich communicates with thehole156band has a diameter smaller than that of thehole156b. Theinsert members200 are inserted at thehole156bwhich constitute part of thegas passing holes156aand are formed on the side toward theintermediate member157.
• The insert members according to the present invention each include a gas passage formed to extend along a direction perpendicular to or at an angle to the central axis of the gas supply hole so as to regulate the flow along the central axis. For instance, a[0064]gas passage202 at theinsert member200 in FIG. 4 is formed in a spiral shape so as to communicate between the upper end and the lower end of theinsert member200 while constantly regulating the flow along the central axis at thegas passing hole156a. In more specific terms, such a gas passage may be achieved by forming a spiral groove at the external circumferential surface of theinsert member200, as shown in FIG. 4A, for instance. Thegas passage202 is formed by this spiral groove and the inner wall of thegas passing hole156aas theinsert member200 is inserted at thegas passing hole156a. It is to be noted that although not shown, the gas passage may instead be formed in a zigzag pattern at the insert member.
• In addition, as shown in FIG. 4B, the[0065]gas passage202 may be formed so that its section has a width (groove depth) along a direction extending perpendicular to the central axis of the gas passing hole, which is larger than the thickness of thegas passing hole156aalong the central axis. As the number of turns of thespiral gas passage202 increases, the entry of charged particles can be prevented with greater effectiveness. However, as the number of turns of thespiral gas passage202 increases, the gas passage becomes narrower, resulting in a lowered flow rate of the processing gas. Accordingly, the number of turns that thespiral gas passage202 makes should be determined so as to strike an optimal balance between the desired level of charged particle entry prevention and the desired processing gas flow rate. For instance, it is desirable to form the spiral gas passage so that it makes 1.5 turns or more at the external side surface of theinsert member200.
• When[0066]such insert members200 are inserted at the individualgas passing holes156a, thegas passages202 of theinsert members200 regulate the flow along the central axes of the individualgas passing holes156aat all times and thus, any charged particles in the plasma that may enter through thegas passing holes156aare bound to collide into the inner walls or the like of theinsert members200 and lose their energy before they reach the upper ends of theinsert members200.
• Furthermore, even if the equipotential line becomes skewed at the end of a[0067]gas passing hole156aand the direction along which charged particles such as electrons oscillate becomes tilted as a result to allow the charged particles to enter through thegas passing hole156a, the flow along the central axis of thegas passing hole156ais regulated by thegas passage202 at all times. Thus, the charged particles collide into the inner wall or the like of theinsert member200 and their energy becomes dissipated before they reach the upper end of theinsert member200.
• Consequently, the charged particles in the plasma are prevented from entering the[0068]buffer chamber160 inside theupper electrode138 with a high degree of effectiveness. With no energy transferred into thebuffer chamber160, it is ensured that a glow discharge does not occur within thebuffer chamber160.
• In addition, since the[0069]gas passage202 of theinsert member200 is formed so that its thickness along the central axis of thegas passing hole156ais smaller than its width (groove depth) along the direction perpendicular to the central axis, as shown in FIG. 4B. The space inside thegas passing hole156aalong the axial direction can be narrowed to cause charged particles such as electrons to readily collide into the wall and the like of theinsert member200 and to lose energy quickly. Furthermore, as the flow rate of the processing gas can be increased, the occurrence of a glow discharge inside theupper electrode138 can be prevented without having to greatly alter the gas outlet characteristics of the upper electrode (shower head)138.
• It is to be noted that the insert members according to the present invention may each be detachably mounted through the entire length of the[0070]gas passing hole156aat theelectrode plate156, as in the case of aninsert member210 shown in FIG. 5. FIG. 5A presents an external view of theinsert member210, whereas FIG. 5B is a sectional view of theinsert member210 mounted at thegas passing hole156a. Agas passage212 of thisinsert member210 may be formed over theentire insert member210, as shown in FIG. 5A, for instance.
• In another specific example of the insert members according to the present invention, the gas passage formed to regulate the flow along the central axis of the gas supply hole and extends along the direction perpendicular to or at an angle to the central axis may be present along both the diameter and the circumference of the insert member. More specifically, it may be provided as an insert member[0071]230 shown in FIGS. 6 and 7. FIG. 6 is a perspective showing the structure adopted in theinsert member220, whereas FIG. 7A and FIG. 7B are both sectional views taken along A-A and B-B in FIG. 6 respectively.
• The[0072]insert member220 is detachably inserted at thehole156bin thegas passing hole156aat theelectrode plate156, as is theinsert member200 shown in FIG. 4. As shown in FIGS. 6 and 7, theinsert member220 has an overall shape of a substantially circular column with acircumferential groove224 formed at a substantially middle portion of the outer side surface.
• At a lower position relative to the[0073]circumferential groove224 of theinsert member220, anaxial hole226 is formed along the axis of thegas passing hole156aand a diameter-direction hole228 is formed along the diameter of thegas passing hole156ato communicate with the upper end of theaxial hole226, as shown in FIG. 7A. The diameter-direction hole228 is in communication with thecircumferential groove224. The diameter-direction hole228 and thecircumferential groove224 together form a passage extending perpendicular to or at an angle to the central axis of the gas supply hole.
• As shown in FIG. 7B, at a position upward relative to the[0074]circumferential groove224 of theinsert member220,axial grooves229 are formed perpendicular to the direction along which the diameter-direction hole228 is formed so as to cut through to the upper end of theinsert member220. The lower ends of theaxial grooves229 are in communication with thecircumferential groove224.
• As the[0075]insert member220 is inserted at thegas passing hole156a, a passage is formed by the individual grooves and the inner wall of thegas passing hole156a. Agas passage222 of theinsert member220 adopting the structure described above extends upward from its lower end along the axial direction through theaxial hole226, passes along the diameter through the diameter-direction hole228 from the upper end of theaxial hole226, makes a 90° turn along thecircumferential groove224 and then extends upward through theaxial grooves229 to the upper end of thegas passage222.
• By inserting this[0076]insert member220 at eachgas passing hole156a, it can be ensured that even if charged particles in the plasma enter thegas passing hole156a, they cannot reach theaxial grooves229 without first advancing along the diameter through the diameter-direction hole228 and then making a 90° turn at thecircumferential groove224. Since the flow in thegas passing hole156aalong its central axis is regulated with the passage extending both along the diameter and along the circumference in this manner, the charged particles are bound to collide into the inner wall or the like of theinsert member220 and lose energy before they reach the upper end of theinsert member220.
• In addition, even if the equipotential line becomes skewed at the end of a[0077]gas passing hole156acausing a tilt in the direction along which charged particles such as electrons oscillate and the charged particles are allowed to enter thegas passing hole156a, the flow in thegas passing hole156aalong the central axis is regulated by thegas passage222 at all times and thus, charged particles are bound to collide into the inner wall or the like of theinsert member220 to lose energy before they reach the upper end of theinsert member220.
• [0078]Such insert members220, too, make it possible to effectively prevent entry of charged particles in the plasma into thebuffer chamber160 at theupper electrode138. As a result, no energy is transferred into thebuffer chamber160 and the occurrence of a glow discharge inside thebuffer chamber160 can be prevented with a high degree of reliability.
• It is to be noted that the dimensions of the section of the[0079]gas passage222 at theinsert member220, too, should be determined so as to strike an optimal balance between the desired level of charged particle entry prevention and the desired processing gas flow rate. More specifically, if the diameter of thegas passing hole156ais approximately 4 mm to 5 mm, it is desirable to set the height of thegas passing hole156aalong the axial direction over the diameter-direction hole228 and thecircumferential groove224 in thegas passage 222 to 0.5 mm to 1.5 mm.
• Next, materials that may be used to constitute the insert members according to the present invention are explained. The[0080]insert members200,210 and220 described above may be constituted of a fluororesin such as Teflon (registered trademark), a tetrafluoroethylene resin (PTFE), a chlorine trifluoroethylene resin (PCTFE), a tetrafluoroethylene parfluoroalkylvynylether copolymer resin (PFA), a tetrafluoroethylene-hexafluoride propylene copolymer resin (PFE) or a fluorovinyllidene resin (PVDF) instead of quartz. These materials are desirable since they have low dielectric constants, achieve a high level of voltage withstanding performance against AC voltages and can be processed with ease, which makes it possible to minimize production costs. Alternatively, the insert members may be constituted of a porous ceramic instead of a resin. Furthermore, theinsert members200 achieved in the embodiment, which are used in the field freeupper electrode138, may instead be constituted of metal, e.g., aluminum, instead of resin.
• The insert members mounted at the gas supply holes in the[0081]upper electrode138 in the embodiment are interchangeable. Accordingly, the optimal type of insert members should be selected in correspondence to various conditions including the gas type and the plasma density to be inserted at the gas supply holes in theupper electrode138. By using the optimal insert members, it is possible to fully prevent charged particles in the plasma generated in theprocessing chamber110 from entering theupper electrode138, which constitutes the gas supply unit.
• More specifically, insert members constituted of different materials may be mounted in correspondence to different types of processing gases. For instance, insert members constituted of polyimide may be used in conjunction with a CF gas, and insert members constituted of PTFE with a high level of corruption resistance may be used in conjunction with a corrosive gas such as a NH3 gas, a HBR gas or a C12 gas.[0082]
• In addition, insert members formed in different shapes may be mounted in correspondence to different density levels of the plasma generated inside the[0083]processing chamber110. For instance, as the plasma density rises, it becomes necessary to more rigorously ensure that charged particles in the plasma cannot enter the upper electrode readily and, accordingly, theinsert members200 or210 having thespiral gas passages202 or212 as shown in FIG. 4 or FIG. 5 should be used, whereas if the plasma density is low, theinsert members220 having thegas passages222 structured as shown in FIGS. 6 and 7 formed therein are good enough.
• As explained in detail above, the present invention provides a plasma processing apparatus with which it is impossible to fully prevent charged particles in plasma generated inside the processing chamber from entering the gas supply unit.[0084]
• While the invention has been particularly shown and described with respect to a preferred embodiment thereof by referring to the attached drawings, the present invention is not limited to this example and it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit, scope and teaching of the invention.[0085]
• For instance, while high-frequency power is applied to the[0086]lower electrode112 alone and theupper electrode138 is grounded in the explanation given above on theplasma processing apparatus100 achieved in the embodiment, the present invention may also be adopted in a plasma processing apparatus in which high-frequency power is also applied to theupper electrode138 as well as to thelower electrode112. In such a case, too, a glow discharge inside theupper electrode138 can be prevented as effectively as in the embodiment.
• In addition, the present invention may be adopted in a plasma processing apparatus other than a plane parallel plasma etching apparatus, such as a helicon wave plasma etching apparatus or an inductively coupled plasma etching apparatus. In more specific terms, the present invention may be adopted in plasma processing apparatuses such as those explained in reference to FIGS.[0087]8 to11 and FIGS. 12 through 21.
• (Another Example of Plasma Processing Apparatus in Which the Present Invention May Be Adopted)[0088]
• Next, another example of a plasma processing apparatus in which the present invention may be adopted is explained in reference to drawings. The plasma processing apparatus in this example is employed to execute specific types of plasma processing such as etching and film formation processing on work substrates, e.g., semiconductor wafers or glass substrates for liquid crystal display devices, by using plasma.[0089]
• It is an established practice in the area of semiconductor device production to process a work substrate such as a semiconductor wafer or a glass substrate for a liquid crystal display device in a desired manner by employing a plasma processing apparatus that executes, for instance, etching processing or film formation processing on the work substrate with plasma generated inside a vacuum chamber and applied onto the work substrate.[0090]
• In the plasma processing apparatus which may be a so-called plane parallel plasma processing apparatus, a stage on which the semiconductor wafer or the like is placed is provided inside the vacuum chamber, a shower head is provided at the ceiling of the vacuum chamber so as to face opposite the stage and a pair of plain parallel electrodes are constituted with the stage and the shower head.[0091]
• A specific type of processing gas is supplied from the shower head into the vacuum chamber and at the same time, the vacuum chamber is evacuated through its bottom so as to fill the vacuum chamber with a processing gas atmosphere achieving a predetermined degree of vacuum. In this state, high-frequency power with a predetermined frequency is supplied between the stage and the shower head, thereby generating plasma with the processing gas, and as the plasma is applied to the semiconductor wafer, the semiconductor wafer is processed, e.g., etched.[0092]
• The plasma processing apparatus in the related art as described above include those having an evacuation ring formed as an annular plate surrounding the stage with numerous permeating hole or slit-shaped evacuating passages formed therein to achieve an even flow of the processing gas around the semiconductor wafer by uniformly evacuating the atmosphere around the stage and to prevent a plasma leak from the processing space (see, for instance, Japanese Utility Model Publication No. 5-8937 (FIGS. 1 through 3)).[0093]
• While the evacuation ring has a function of preventing a plasma leak from the processing space within the vacuum chamber, as described above, it is necessary to ensure that electrons are not allowed to pass through the evacuating passages readily by reducing the opening area of the evacuating passages or increasing the length of the evacuating passages in the evacuation ring in order to further improve the plasma leak preventing effect. It is to be noted that if a plasma leak occurs, the plasma becomes unstable and it becomes difficult to execute a specific type of plasma processing on the semiconductor wafer or the like. For this reason, the likelihood of a plasma leak needs to be minimized.[0094]
• However, if the function of the evacuation ring for preventing plasma leak is improved as described above, it becomes more difficult to achieve a sufficient level of conductance of the gas. This gives rise to a problem in that with the evacuation performance becoming poor, the processes that can be executed become limited. If, on the other hand, priority is given to high evacuation performance in order to avoid the problem discussed above, it becomes necessary to use a large high-performance vacuum pump to result in an increase in the apparatus production costs.[0095]
• As described above, if the function of the evaluation ring for preventing a plasma leak is improved, the conductance of the gas becomes poor, and it is difficult to satisfy both the requirements for the plasma leak preventing function and the sufficient level of conductance of the gas in the plasma processing apparatus in the related art. This leads to problems in that a desired type of plasma processing cannot be executed due to the occurrence of a plasma leak and in that the processes which can be executed become limited due to poor conductance of the gas and the like.[0096]
• Accordingly, an object of the present invention, which has been completed by addressing the problems discussed above, is to provide a plasma processing apparatus having a high level of gas conductance capacity to enable a wide range of processes without increasing the production costs and also having an effective plasma leak preventing function to allow plasma processing to be executed in a desirable manner with stable plasma.[0097]
• In order to achieve the object described above, in an aspect of the present invention, a plasma processing apparatus comprising a vacuum chamber in which a work substrate is placed, a stage disposed within the vacuum chamber on which the work substrate is placed, a plasma generating mechanism that generates plasma within the vacuum chamber to be used to execute a specific type of processing on the work substrate, an evacuation ring disposed so as to surround the stage and having an evacuating passage formed therein and an evacuation mechanism that evacuates the vacuum chamber via the evacuating passage, characterized in that the evacuation ring includes a side wall portion formed substantially perpendicular to the surface of the stage on which the work substrate is placed and a bottom portion ranging inward from the lower end of the side wall portion and in that the evacuating passage is formed at least at the side wall portion, is provided.[0098]
• The side wall portion of the evacuation ring is constituted with an inner cylindrical member and an outer cylindrical member disposed coaxially to each other over a predetermined distance from each other, which should be positioned so as to offset an opening at the inner cylindrical member and an opening at the outer cylindrical member from each other.[0099]
• In this structure, the opening at the inner cylindrical member and the opening at the outer cylindrical member may be formed in a longitudinally elongated rectangular shape, and the inner cylindrical member and the outer cylindrical member may each have a plurality of such openings set along the circumferential direction over predetermined intervals.[0100]
• In addition, the evacuating passage may be formed with the opening formed at the inner cylindrical member, a clearance formed between the inner cylindrical member and the outer cylindrical member and the opening formed at the outer cylindrical member.[0101]
• Also, the evacuating passage may be formed at the bottom portion of the evacuation ring in the plasma processing apparatus.[0102]
• In another aspect of the present invention, the object described above is achieved by providing a plasma processing apparatus comprising a vacuum chamber in which a work substrate is placed, a stage disposed within the vacuum chamber on which the work substrate is placed, a plasma generating mechanism that generates plasma inside the vacuum chamber to be used to execute a specific type of processing on the work substrate, an evacuation ring disposed so as to surround the stage and having an evacuating passage formed therein and an evacuation mechanism that evacuates the vacuum chamber from the bottom of the evacuation ring via the evacuating passage, characterized in that the evacuation ring includes a first member having a first opening and a second member disposed over a distance with a clearance formed between the first member and the second member and having a second opening formed at a position offset from the first opening, in that the evacuating passage is formed to extend from the first opening into the clearance and pass through the clearance to be led out from the second opening and in that the plasma is trapped inside the clearance.[0103]
• The present invention achieved in an embodiment is now explained in detail in reference to drawings. FIG. 8 is a schematic illustration of the structure adopted in the embodiment achieved by adopting the present invention in a plane parallel plasma etching apparatus used to etch semiconductor wafers. In FIG. 8,[0104]reference numeral301 indicates a cylindrical vacuum chamber constituted of, for instance, aluminum and having an internal space that can be closed off in an airtight state.
• A[0105]stage302 on which a semiconductor wafer W is placed is provided inside thevacuum chamber301, and thestage302 also functions as a lower electrode. At the ceiling inside thevacuum chamber301, ashower head303 constituting an upper electrode is disposed and a pair of plain parallel electrodes are constituted by thestage302 and theshower head303.
• A[0106]free space304 in which the gas is diffused is formed at theshower head303 and numerousnarrow holes305 are formed on the lower side relative to thefree space304 for gas diffusion. A specific type of processing gas supplied from a processinggas supply system306 is diffused inside thefree space304 for gas diffusion, and the diffused processing gas is then supplied in a shower directed toward the semiconductor wafer W through thenarrow holes305. While the potential at theshower head303 is set to the ground level in the embodiment, a high-frequency source may be connected to theshower head303 to apply high-frequency power both to thestage302 and to theshower head303, instead.
• Two high-[0107]frequency sources309 and310 are connected to thestage302 via twomatchers307 and308 respectively and, as a result, high-frequency power can be supplied to thestage302 by superimposing the high frequency power with one of the two different specific frequencies (e.g., 100 MHz and 3.2 MHz) on the high frequency power with the other frequency. It is to be noted that a single high-frequency source may be used to supply high-frequency power to thestage302 so that high-frequency power with a single frequency is supplied to thestage302, instead.
• In addition, an[0108]electrostatic chuck311 which electrostatically holds the semiconductor wafer W is provided at the surface of thestage302 on which the semiconductor wafer W is placed. Theelectrostatic chuck311 adopts a structure achieved by disposing anelectrostatic chuck electrode311binside an insulatinglayer311a, with a DC source312 connected to theelectrostatic chuck electrode311b. Afocus ring313 is provided at the upper surface of thestage302 so as to surround the semiconductor wafer W.
• An[0109]evacuation port314 is provided at the bottom of thevacuum chamber301, and anevacuation system315 constituted of a vacuum pump and the like is connected to theevacuation port314.
• An[0110]evacuation ring316 formed in an annular shape is provided around thestage302. As shown in FIG. 9, theevacuation ring316 includes aside wall portion317 formed to range downward almost perpendicularly and abottom portion318 ranging inward perpendicular to the bottom end of theside wall portion317.
• As shown in FIG. 10, the[0111]side wall portion317 is constituted with an innercylindrical member319 and an outercylindrical member320 disposed, coaxially to each other over a predetermined distance from each other. The innercylindrical member319 includes a plurality ofopenings319aformed in a vertically elongated rectangular shape and set over specific intervals along the circumferential direction to constitute evacuating passages. In addition, as shown in FIGS. 10 and 14, the outercylindrical member320, too, includes a plurality ofopenings320aformed in a vertically elongated rectangular shape to constitute the evacuating passages. Theopenings319aand theopenings320aare disposed so that they are offset from each other by a predetermined extent (by the distance C in FIG. 11) along the circumferential direction.
• The evacuating passages are thus each formed so that the gas passes through the[0112]openings319aat the innercylindrical member319, then passes through aclearance321 formed between the innercylindrical member319 and the outercylindrical member320 and subsequently is discharged through theopenings320aat the outercylindrical member320, as the arrows in FIG. 11 indicate.
• The dimensions A to D in FIG. 11, i.e., the width A of the[0113]clearance321, the width B of theopenings319a, the width C over which theopenings319aare offset relative to the correspondingopenings320aand the thickness D of the innercylindrical member319 satisfy the following conditions:
• C/A>1[0114]
• B>2A[0115]
• B/D>1[0116]
• Namely, the[0117]evacuation ring316 achieves a structure that traps plasma in theclearance321, and in order to assure this, the width A of theclearance321 is set relatively small, whereas the offset width C of theopenings319aand theopenings320ais set large enough to trap the plasma.
• In addition, the width B of the[0118]openings319a, which are not used to trap the plasma, is set to a large value to ensure a high enough conductance level with a large opening area, and for the same reason, the thickness D of the innercylindrical member319 is set to a small value. The thickness of the outercylindrical member320 and the width of theopenings320a, too, are set to similar values based upon the same principle.
• It is to be noted that FIG. 11 schematically illustrates the structure of the[0119]evacuation ring316 and it does not indicate the actual dimensions accurately. In the actual application, the width B of theopenings319ais set greater than 2 mm, e.g., approximately several millimeters if, for instance, the width A of theclearance321 is set to 1 mm. The offset width C of theopenings319aand theopenings320aand the thickness D of the innercylindrical member319 are also set to values conforming to the conditions presented earlier and taking machinability into consideration.
• The length of the[0120]side wall portion317 along the vertical direction, too, is set to a value that will allow theopenings319aand theopenings320ato range over large enough areas and assures a satisfactory level of conductance.
• By forming evacuating passages at the[0121]side wall portion317 of theevacuation ring316 and setting the length of theside wall portion317 along the vertical direction to a relatively large value, as described above, the openings are allowed to range over large enough areas and thus a satisfactory level of conductance is assured. In addition, since the diameter of theevacuation ring316 does not need to be increased even though the openings range over great areas, the diameter of thevacuum chamber301 itself does not need to increase, and thus, the footprint of the apparatus remains unchanged.
• Furthermore, by forming the evacuating passages at the[0122]side wall portion317 with theopenings319a, theclearance321 and theopenings320aas described above, the openings are allowed to range over large areas to assure a satisfactory level of conductance while assuring the required plasma leak preventing function, as well.
• In other words, while electrons in the plasma are allowed to pass through the[0123]openings319aranging over large areas in the gas flow indicated by the arrows in FIG. 11, the outercylindrical member320 is present ahead as the electrons advance and thus, the likelihood of the electrons further passing through theclearance321 and being led out to the outside through theopenings320ais greatly lowered. Namely, since the plasma is highly unlikely to leak to the outside of theopenings320a, a satisfactory level of plasma leak preventing function can be assured even when the openings range over large areas to achieve a high level of conductance.
• Moreover,[0124]numerous openings318aeach constituted as a circular hole are formed at thebottom portion318 of theevacuation ring316 as well, and theseopenings318a, too, form evacuating passages in the embodiment. By forming evacuating passages at thebottom portion318 in this manner, the conductance can be further improved.
• Instead of forming the evacuating passages at the[0125]bottom portion318 of theevacuation ring316 with openings such as circular holes as described above, the evacuating passage at thebottom portion318, may adopt a structure identical to that of the evacuating passages at theside wall portion317. However, since thebottom portion318 is located at a considerable distance from the area in which plasma is formed, the evacuating passage at thebottom portion318 can be formed with simple circular holes or the like without having to consider the plasma leak preventing function as a crucial factor. In addition, if a sufficiently high level of conductance can be assured with the evacuating passages formed at theside wall portion317 alone, no evacuating passages need to be formed at thebottom portion318.
• The[0126]evacuation ring316 described above may be formed by using any material as long as it is electrically conductive and may be constituted of, for instance, stainless steel or aluminum with an alumite film or a sprayed coating deposited on the surface thereof. Theevacuation ring316 constituted of a conductive material is electrically connected to the ground potential.
• As the[0127]vacuum chamber301 is evacuated through theevacuation port314 via theevacuation ring316 adopting the structure described above by utilizing theevacuation system315, the atmosphere inside thevacuum chamber301 achieves a predetermined degree of vacuum.
• Furthermore, a magnetic[0128]field forming mechanism322 is provided around thevacuum chamber301 so as to form a desired magnetic field in the processing space inside thevacuum chamber301. The magneticfield forming mechanism322 includes arotating mechanism323, and as the magneticfield forming mechanism322 is rotated around thevacuum chamber301, the magnetic field inside thevacuum chamber301, too, is allowed to rotate.
• Next, an etching process executed in the plasma etching apparatus structured as described above is explained. First, a gate valve (not shown) at a transfer port (not shown) is opened, and a semiconductor wafer W carried into the[0129]vacuum chamber301 with a transfer mechanism or the like is set on thestage302. The semiconductor wafer W placed on thestage302 is then electrostatically held onto theelectrostatic chuck311 by applying a predetermined level of a DC voltage to theelectrostatic chuck electrode311bof theelectrostatic chuck311 from the D.C. source312.
• Next, after moving the transfer mechanism out of the[0130]vacuum chamber301, the gate valve is closed, thevacuum chamber301 is evacuated with the vacuum pump or the like of theevacuation system315, and then, after a specific degree of vacuum is achieved inside thevacuum chamber301, the processing gas to be used to execute a specific type of etching process is supplied from the processinggas supply system306 into thevacuum chamber301 via thefree space304 for gas diffusion and thenarrow holes305 at a flow rate of, for instance, 100 to 1000 sccm. Thus, the pressure inside thevacuum chamber301 is sustained at, for instance, approximately 1.33 to 133 Pa (10 to 100 mTorr).
• In this state, high-frequency power with specific frequencies (e.g., 100 MHz and 3.2 MHz) is supplied to the[0131]stage302 from the high-frequency sources309 and310.
• As the high-frequency power is applied to the[0132]stage302 as described above, a high-frequency electric field is formed in the processing space between theshower head303 and thestage302. In addition, a specific magnetic field is formed in the processing space by the magneticfield forming mechanism322. Thus, a plasma with specific characteristics is generated from the processing gas supplied into the processing space, and a specific film on the semiconductor wafer W becomes etched with the plasma.
• During this process, the high conductance at the[0133]evacuation ring316 makes it possible to evacuate the vacuum chamber with a high degree of efficiency and, as a result, the atmosphere inside the vacuum chamber easily achieves a high degree of vacuum without having to employ a large, high performance vacuum pump or the like. In addition, since a plasma leak can be prevented with a high degree of reliability at theevacuation ring316, the desired etching process can be executed with a high level of accuracy with stable plasma.
• After the specific etching process is executed, the supply of the high-frequency power from the high-[0134]frequency sources309 and310 is stopped, thereby ending the etching process, and then, the semiconductor wafer W is carried out of thevacuum chamber301 by reversing the procedure described earlier.
• It is to be noted that while the present invention is adopted in a plasma etching apparatus that etches semiconductor wafers in the embodiment described above, the present invention is not limited to this example. For instance, it may be adopted in an apparatus that processes substrates other than semiconductor wafers, or in an apparatus that executes processing other than etching, e.g., a film formation processing apparatus that executes CVD or the like.[0135]
• The plasma processing apparatus described above achieving a high level of gas conductance capability supports a wide range of processes without necessitating an increase in the production costs and enables the plasma processing to be executed in a desirable manner with stable plasma achieved through its high level of plasma leak preventing function.[0136]
• (Another Example of a Plasma Processing Apparatus in Which the Present Invention May Be Adopted)[0137]
• Next, yet another example of the plasma processing apparatus in which the present invention may be adopted is explained. The present invention is adopted in a plasma processing apparatus that executes plasma processing on workpieces that may be glass substrates for flat displays (FPD) such as liquid crystal displays (LCD), i.e., FPD substrates such as LCD substrates, as well as semiconductor wafers in this example. More specifically, an explanation is given in reference to the example on a plasma processing apparatus capable of implementing control so as to drive a member such as an electrode disposed within the plasma processing apparatus to a desired position and its upper electrode unit.[0138]
• In a plasma processing apparatus that executes plasma processing on a workpiece such as a semiconductor wafer (hereafter simply referred to as a wafer) or an LCD substrate during various processes of semiconductor devices or LCD substrate production, follow-up control is normally implemented by utilizing a servomotor, a stepping motor or the like as an actuator to implement control so as to linearly drive a member such as an a electrode disposed within the processing apparatus to a desired position.[0139]
• In such a structure having a motor utilized as an actuator, a sturdy structural body is required to form a motive force communicating mechanism constituted of a pulley, gears, a belt or a chain to be used to convert the motor rotation to a linear motion, and thus, the processing apparatus itself is bound to be large in size. In addition, there is also a problem in that vibration and noise caused by the rotational motion of the motor and the motive force communicating mechanism adversely affect the results of the wafer processing. Furthermore, it requires a regular maintenance since the gears and the chain constituting the motive force communicating mechanism are consumables.[0140]
• While it is conceivable to utilize an actuator constituted of a pneumatic actuator instead of a motor, the piping connection for a pneumatic actuator is bound to be complex and there is also the concern that an oil leak may cause contamination in the clean room. For these reasons, a pneumatic actuator is not suitable for an application in a plasma processing apparatus.[0141]
• As an alternative, a pneumatic actuator may be utilized as the actuator. A pneumatic actuator is advantageous in that there is no risk of an oil leak or contamination of the clean room. There is another advantage to the pneumatic actuator in that it can be provided as a light weight, compact unit capable of achieving a high output. For these reasons, pneumatic actuators are used in plasma processing apparatus applications, in a wafer cassette elevator mechanism (see, for instance, the Japanese Patent Laid-open Publication No. 2001-35897) and in a gate switching mechanism (see, for instance, Japanese Patent Laid-open Publication No. 10-209245 (U.S. Pat. No. 6,113,734)) provided at the wafer transfer port in the processing chamber.[0142]
• However, when a pneumatic actuator is used as the actuator to implement control on the drive of a member disposed inside the plasma processing apparatus, the compressibility due to the material characteristics inherent to air such as the viscosity and density, and the nonlinearity attributable to the communication delay compromise the control performance. In addition, the control performance is also affected by external factors such as the temperature. Thus, highly accurate positional control, in particular, cannot easily be achieved with a pneumatic actuator.[0143]
• For this reason, a pneumatic actuator is primarily utilized in simple tasks such as a constant repetitive operation and is not deemed suitable for drive control of, for instance, an electrode, in which highly accurate positional control must be achieved in the related art.[0144]
• Accordingly, an object of the present invention, which has been completed by addressing the problems discussed above, is to provide a plasma processing apparatus and an upper electrode unit with which highly accurate positional control can be implemented by using a pneumatic actuator.[0145]
• In order to achieve the object described above, in a first aspect of the present invention, a plasma processing apparatus that executes plasma processing on a workpiece with plasma generated by using an electrode disposed inside a processing container, comprising a sliding support member that slidably supports the electrode with a slide mechanism so that the electrode is allowed to slide freely along one direction, a pneumatic cylinder having a rod disposed continuous with the sliding support member, a pneumatic circuit that drives the pneumatic cylinder and a means for control that implements positional control of the electrode by controlling the pneumatic circuit, is provided.[0146]
• A second aspect of the present invention achieves the object by providing an upper electrode unit of a plasma processing apparatus that executes plasma processing on a workpiece with plasma generated by using an upper electrode disposed inside a processing container, comprising the upper electrode disposed inside the processing container, a sliding support member that slidably supports the upper electrode with a slide mechanism so as to allow the upper electrode to slide freely along the vertical direction, a pneumatic cylinder having a rod disposed continuous to the sliding support member, a pneumatic circuit that drives the pneumatic cylinder and a means for control that implements positional control of the upper electrode by controlling the pneumatic circuit.[0147]
• According to the invention achieved in the first aspect and the second aspect by adopting the structure described above, the sliding support member provided independently of the pneumatic cylinder slidably supports the electrode so as to allow the electrode to slide freely along one direction (e.g., the vertical direction) and, as a result, any load (external disturbance) that would otherwise be applied to the pneumatic cylinder along a direction other than the one direction is eliminated to engage the pneumatic cylinder in movement along one direction exclusively. Consequently, highly accurate positional control of the electrode is achieved with the pneumatic cylinder.[0148]
• In addition, by providing the upper electrode, the drive mechanism of the upper electrode and the means for its control as an integrated unit as in the second aspect, the upper electrode unit can be installed into an existing plasma processing apparatus with ease to achieve positional control for the upper electrode with a pneumatic cylinder.[0149]
• The slide mechanism used in the first and second aspects may include a rail disposed at the external circumference of the sliding support member along the direction in which electrode slides and a guide member that guides the rail along the sliding direction while supporting the rail slidably and is fixed to the processing container. By adopting such a slide mechanism, the electrode can be slidably supported through a simple structure. The guide member in this slide mechanism may be fixed to the processing container via a horizontal adjustment member of the electrode. In such a case, a fine adjustment of the electrode along the horizontal direction can be achieved readily by adjusting the inclination of the guide member with the horizontal adjustment member.[0150]
• Also, the rod of the pneumatic cylinder used in the first and second aspects may be disposed at an approximate center of the electrode. This structure is effective in preventing decentering of a load applied to the rod of the pneumatic cylinder and suppressing an occurrence of moment, and thus, even more accurate positional control of the electrode is achieved.[0151]
• Furthermore, the pneumatic circuit used in the first and second aspects may include a switching valve provided at a position between a pneumatic source and the pneumatic cylinder, which enable drive of the rod of the pneumatic cylinder by switching the flow of compressed air supplied to the pneumatic cylinder based upon a control signal provided by the means for control and a drive stop valve disposed at a position between the switching valve and the pneumatic cylinder, which allows the rod of the pneumatic cylinder to stop and be held by cutting off the compressed air supplied to the pneumatic cylinder based upon a stop signal provided by the means for control. By adopting such a structure in the pneumatic circuit, it becomes possible to control the position to which the electrode moves and the direction along which the electrode moves with the means for control, and thus, if an abnormality occurs in the plasma processing apparatus, the movement of the electrode can be stopped and the electrode can be held at the stop position.[0152]
• In addition, a means for positional detection that detects the position of the electrode by detecting the movement of the rod at the pneumatic cylinder used in the first and second aspects may be provided to allow the means for control to implement the positional control of the electrode based upon a deviation determined by subtracting the current position of the electrode detected with the means for positional detection from a target position set for the electrode. In such a case, the target position may be set over a plurality of stages leading to the position to which the electrode is to be ultimately moved, so as to drive the electrode gradually. By driving the electrode gradually in this manner, the occurrence of abrupt drive and vibration caused by material characteristics inherent to the air used to drive the pneumatic cylinder such as the viscosity and the density can be minimized. Thus, while the upper electrode is driven with the pneumatic cylinder, problems such as attracting particles and the like in the processing container, for instance, can be prevented.[0153]
• It is to be noted that the electrode referred to in the description of the first aspect is one of a pair of electrodes disposed parallel to each other inside the processing container, and the workpiece may be placed on the other electrode.[0154]
• The following is a detailed explanation of a preferred embodiment of the present invention, given in reference to attached drawings. It is to be noted that in the specification and the drawings, the same reference numerals are assigned to components having substantially identical functions and structural features to preclude the necessity for a repeated explanation thereof.[0155]
• FIGS. 12 and 13 schematically illustrates the structure adopted in a plane parallel[0156]plasma processing apparatus400, which is a typical example of the plasma processing apparatus achieved in the embodiment of the present invention. FIG. 12 shows the upper electrode set at the retracted position, whereas FIG. 13 shows the upper electrode set at the processing position. FIG. 14 schematically illustrates the mechanism used to drive the upper electrode shown in FIGS. 12 and 13 to facilitate an explanation of its functions, with FIG. 14A showing a state in which the upper electrode is set at the retracted position and FIG. 14B showing a state in which the upper electrode is set at the processing position.
• The[0157]plasma processing apparatus400 achieved in the embodiment includes a cylindrical chamber (processing container)402 constituted of aluminum with a surface thereof having undergone anodization (alumite processing), and thechamber402 is grounded.
• A[0158]susceptor stage404 formed in a substantially columnar shape, on which a workpiece such as a semiconductor wafer (a hereafter simply referred to as a “wafer”) W is placed is provided at the bottom inside thechamber402 via an insulatingplate403 constituted of ceramic or the like. Asusceptor405 constituting a lower electrode is set on thesusceptor stage404. A high pass filter (HPF)106 is connected to thesusceptor405.
• Inside the[0159]susceptor stage404, a temperature adjustmentmedium chamber407 is formed. A temperature adjustment medium which is guided into the temperature adjustmentmedium chamber407 via asupply pipe408 is made to circulate within the temperature adjustmentmedium chamber407 and then is discharged through adischarge pipe409. With the temperature adjustment medium circulating in this manner, the temperature of thesusceptor405 is adjusted to a desired level.
• An[0160]electrostatic chuck411 assuming a shape substantially identical to that of the wafer W is disposed on the central portion of thesusceptor405 on the upper side, which is formed as a projecting disk. Theelectrostatic chuck411 is achieved by setting anelectrode412 between insulating members. A DC voltage at, for instance, 1.5 kV is applied to theelectrostatic chuck411 from aDC electrode413 connected to theelectrode412. As a result, the wafer W becomes electrostatically held onto theelectrostatic chuck411.
• At the insulating[0161]plate403, thesusceptor stage404, thesusceptor405 and theelectrostatic chuck411, agas passage414 through which a heat transfer medium (e.g., a back side gas such as an He gas) is supplied to the rear surface of the workpiece i.e., the wafer W, is formed. The heat is transferred between the susceptor405 and the wafer W via the heat transfer medium, thereby sustaining the temperature of the wafer W at a predetermined level.
• An[0162]annular focus ring415 is disposed at the edge of thesusceptor405 at its upper end so as to surround the wafer W placed on theelectrostatic chuck411. Thefocus ring415 is constituted of an insulating material such as ceramic or quartz, or an electrically conductive material. The presence of thefocus ring415 improves the etching uniformity.
• An[0163]evacuation pipe431 is connected at the bottom of thechamber402, and anevacuation device435 is connected to theevacuation pipe431. Theevacuation device435, which includes a vacuum pump such as a turbo molecular pump, adjusts the pressure of the atmosphere inside thechamber402 to a predetermined lower level (e.g., 0.67 Pa or lower). In addition, agate valve432 is provided at the side wall of thechamber402. As thegate valve432 opens, a transfer of the wafer W into/out of thechamber402 is enabled. It is to be noted that the wafer W is transferred with, for instance, a transfer arm.
• In addition, an[0164]upper electrode420 is disposed above thesusceptor405 to run parallel to thesusceptor405 and to face opposite thesusceptor405. Theupper electrode420 can be driven along one direction, e.g., the vertical direction, by an upperelectrode drive mechanism500. Thus, the distance between the susceptor405 and theupper electrode420 can be adjusted. It is to be noted that the upperelectrode drive mechanism500 is to be described in detail later.
• The[0165]upper electrode420 is supported at the inner wall of the ceiling of thechamber402 via a bellows422. The bellows422 is mounted at the inner wall at the ceiling of thechamber402 with a fastening means such as a bolt via an annularupper flange422aand is also attached to the upper surface of theupper electrode420 with a fastening means such as a bolt via andown flange422b.
• The[0166]upper electrode420 includes anelectrode plate424 constituting a surface facing opposite thesusceptor405 and having numerous outlet holes423 and anelectrode support member425 that supports theelectrode plate424. Theelectrode plate424 is constituted of, for instance, quartz, whereas theelectrode support member425 is constituted of an electrically conductive material such as aluminum with a surface thereof having undergone alumite processing.
• A[0167]gas supply port426 is provided at theelectrode support member425 of theupper electrode420. Agas supply pipe427 is connected to thegas supply port426. In addition, a processinggas supply source430 is connected to thegas supply pipe427 via avalve428 and amass flow controller429.
• An etching gas, for instance, to be used to execute plasma etching is supplied from the processing[0168]gas supply source430. It is to be noted that while FIG. 12 shows a single processing gas supply system comprising thegas supply pipe427, thevalve428, themass flow controller429, the processinggas supply source430 and the like, theplasma processing apparatus400 includes a plurality of processing gas supply systems in reality. Namely, CHF8, Ar and He, for instance, to constitute to the processing gas, the flow rates of which are controlled independently of one another, are individually supplied into thechamber402.
• A first high-[0169]frequency source440 is connected to theupper electrode420, with afirst matcher441 inserted at the power supply line. In addition, a low pass filter (LPF)442 is connected to theupper electrode420. The first high-frequency source440 is capable of outputting power at a frequency in the range of 50 to 150 MHz. As the power at such a high-frequency is applied to theupper electrode420, high-density plasma can be formed in a desired state of dissociation inside thechamber402 and plasma processing can be executed at a lower pressure compared to the related art. Ideally, the frequency of the power output from the first high-frequency source440 should be 50 to 80 MHz, and typically, it is adjusted to 60 MHz as shown in the figure or to a value close to 60 MHz.
• A second high-[0170]frequency source450 is connected to thesusceptor405 constituting the lower electrode, with asecond matcher451 inserted at the power supply line. The second high-frequency source450 is capable of outputting power at a frequency in the range of several hundred kHz to several tens of MHz. As the power at a frequency in this range is applied to thesusceptor405, a desired ionization effect can be achieved without damaging the workpiece, i.e., the wafer W. Typically, the frequency of the power output from the second high-frequency source450 is adjusted to 2 MHz, as shown in the figure, or to 13.56 MHz.
• Next, the upper[0171]electrode drive mechanism500 is explained in detail. The upperelectrode drive mechanism500 includes a substantially cylindrical slidingsupport member504 that slidably supports theupper electrode420 so as to allow theupper electrode420 to slide relative to thechamber402. The slidingsupport member504 is mounted at an approximate center of the top surface of theupper electrode420 with a bolt or the like.
• The sliding[0172]support member504 is disposed so that it is allowed to freely enter and withdraw from ahole402aformed at an approximate center of the upper wall of thechamber402. More specifically, the external circumferential surface of the slidingsupport member504 is slidably supported at the edge of thehole402aat thechamber402 via aslide mechanism510.
• The[0173]slide mechanism510 includes aguide member516 retained at a vertical portion of a retainingmember514 having an L-shaped section and disposed, for instance, at the top of thechamber402 and arail portion512 slidably supported by theguide member516 and formed to extend along one direction (the vertical direction in the embodiment) at the external circumferential surface of the slidingsupport member504.
• The retaining[0174]member514, which securely retains theguide member516 of theslide mechanism510 includes a horizontal portion fixed to the top of thechamber402 via an annularhorizontal adjustment plate518. Thehorizontal adjustment plate518 is used to adjust the horizontal position of theupper electrode420. Thehorizontal adjustment plate518 may be secured onto thechamber402 with a plurality of bolts or the like set over uniform intervals along the circumferential direction so as to adjust the extent of inclination of thehorizontal adjustment plate518 along the horizontal direction in correspondence to the extents to which the individual bolts protrude. As the inclination of theguide member516 at theslide mechanism510 along the vertical direction is adjusted by adjusting the inclination of thehorizontal adjustment plate518 along the horizontal direction, the inclination of theupper electrode420 supported via theguide member516 is adjusted along the horizontal direction. As a result, it is possible to retain theupper electrode420 at the correct horizontal position at all times through a simple operation.
• A[0175]pneumatic cylinder520 used to drive theupper electrode420 is mounted on the upper side of thechamber402 via abarrel body501. Namely, the lower end of thebarrel body501 is mounted by assuring air tightness with a bolt or the like so as to cover thehole402aat thechamber402 and the upper end of thebarrel body501 is mounted by assuring air tightness at the lower end of thepneumatic cylinder520.
• The[0176]pneumatic cylinder520 includes arod502 that can be driven along one direction, and the lower end of therod502 is disposed continuous to an approximate center area on the upper side of the slidingsupport member504 with a bolt or the like. Thus, as therod502 of thepneumatic cylinder520 is driven, theupper electrode420, too, is driven by the slidingsupport member504 along the slide mechanism in one direction. As the inner space of therod502 assuming a cylindrical shape comes into communication with a central hole formed at an approximate center of the slidingsupport member504, the rod is set in a state of communication with the atmosphere. Thus, the power supply line from thematcher441 or the like can be connected to theupper electrode420 through the inner space of therod502 via the central hole at the slidingsupport member504.
• In addition, a means for positional detection such as a[0177]linear encoder505 that detects the position of theupper electrode420 is provided to the side of thepneumatic cylinder520. Anupper end member507 having anextension507aextending sideways from therod502 is provided at the upper end of therod502 of thepneumatic cylinder520, and adetection portion505aof thelinear encoder505 is in contact with theextension507aof theupper end member507. Since theupper end member507 interlocks with the movement of theupper electrode420, the position of theupper electrode420 can be detected with thelinear encoder505.
• The[0178]pneumatic cylinder520 is constituted by enclosing a tubular cylindermain body522 with anupper support plate524 and alower support plate526. Anannular partitioning member508 that partitions the inner space of thepneumatic cylinder520 into anupper space532 and alower space534 is disposed on the external circumferential surface of therod502.
• As shown in FIG. 14, compressed air is supplied into the[0179]upper space532 of thepneumatic cylinder520 from anupper port536 at theupper support plate524. Compressed air is also supplied into thelower space534 of thepneumatic cylinder520 from alower port538 at thelower support plate526. By controlling the quantities of air supplied into theupper space532 and thelower space534 from theupper port536 and thelower port538 respectively, the drive of therod502 along the one direction (the vertical direction in this example) can be controlled. The quantities of air supplied into thepneumatic cylinder520 are controlled at apneumatic circuit610 provided near thepneumatic cylinder520.
• Next, a means for[0180]drive control600 provided in the plasma processing apparatus in the embodiment as part of the upperelectrode drive mechanism500 is explained. FIG. 15 is a circuit diagram of the means fordrive control600 provided as part of the upperelectrode drive mechanism500 and FIG. 16 is a block diagram of thepneumatic circuit610.
• As shown in FIG. 15, the means for[0181]drive control600 is constituted with thepneumatic circuit610 and a means forcontrol700 that controls thepneumatic circuit610. The means forcontrol700 includes a CPU (central processing unit)720 constituting the main body of the means forcontrol700, aninterface740 that exchanges various signals with the external apparatuses, aninterlock circuit760 used to execute a self diagnosis of thepneumatic circuit610 and the like. Theinterface740 exchanges control signals with a control device (not shown) that controls theplasma processing apparatus400 and also receives sensor signals from various sensors. The signals input to theinterface740 include an upper electrode drive control signal containing target position information used to drive theupper electrode420 to a specific target position and the like, a gate valve control signal used to control the gate valve and sensor signals from the various sensors. In addition, the signals output from theinterface740 include an upper electrode position stable signal indicating whether or not the position of theupper electrode420 has stabilized and whether or not the movement of theupper electrode420 has been completed and a wafer transfer signal indicating whether or not theupper electrode420 is set at a position out of the transfer path of the transfer arm transferring a wafer and thus the wafer can be safely transferred into thechamber402.
• The sensor signals include a signal from an origin point sensor that detects whether or not the[0182]upper electrode420 is positioned at the origin point. The origin point as referred to in this context is the origin point of the means for upper electrode positional detection such as thelinear encoder505. In more specific terms, the origin point sensor may be constituted with, for instance, a contact sensor or an optical sensor. In such a case, the origin point sensor may be disposed on the inner side of the upper wall constituting thebarrel body501 on thechamber402, and the position at which the origin point sensor detects the upper end of the slidingsupport member504, i.e., the uppermost position of theupper electrode420, may be set as the origin point. Another sensor signal input to theinterface740 is a transfer verification position sensor signal inquiring whether or not theupper electrode420 is set at a position that allows a wafer transfer. In response to the transfer verification position sensor signal input to theinterface740, theCPU720 detects whether or not theupper electrode420 is currently set at a position, i.e., a retracted position, at which theupper electrode420 is out of the way of the transfer arm transferring the wafer based upon the detection signal provided by thelinear encoder505 and outputs a wafer transfer signal via theinterface740.
• The[0183]interlock circuit760, to which a signal from aswitch620 that detects whether or not compressed air is output from apneumatic source605 in thepneumatic circuit610 to drive theupper electrode420 is input, outputs a drive enabled signal to thepneumatic circuit610 if compressed air is output from thepneumatic source605, i.e., if the signal from theswitch620 indicates an ON state. If, on the other hand, no compressed air is output from thepneumatic source605, i.e., if the signal from theswitch620 indicates an OFF state, it stops the output of the drive enabled signal to thepneumatic circuit610.
• In addition, the[0184]interlock circuit760 stops the output of the drive enabled signal to thepneumatic circuit610 if an external interlock signal is input even when the signal from theswitch620 indicates an ON state. The interlock signal is input from the control device (not shown) to the means forcontrol700 when, for instance, an abnormality necessitating the drive of theupper electrode420 to be stopped occurs in theplasma processing apparatus400.
• The[0185]CPU720 controls thepneumatic circuit610 based upon the signals from theinterface740. It controls the movement of theupper electrode420 so as to position theupper electrode420 at the target position through feedback control achieved by implementing PID control (control executed by combining a proportional operation, a differential operation and an integration operation) as indicated in the block diagram in FIG. 16, for instance. In the block diagram shown in FIG. 16, Ref (s) is the target position for theupper electrode420 and Y(s) is the current position. G(s) is the transfer function, and KP, KI, KD, KAand KVrespectively indicate the proportional gain, the integral gain, the differential gain, the acceleration feedback gain and the velocity feedback gain.
• More specifically, the deviation is determined by subtracting the current position from the target position set for the[0186]upper electrode420, and PID control is implemented based upon an output (which can be adjusted in correspondence to the integral gain KI) in proportion to the time integral of the deviation and used to correct the steady state deviation, an output (which can be adjusted in correspondence to the differential gain KD) in proportion to the time-varying change in the deviation and used to minimize the change rate and an output (which can be adjusted in correspondence to the proportional gain KP) in proportion to the deviation. Namely, in this PID control, a function of predicting the movement which is in proportion to the current deviation (a proportional operation), a function of eliminating the offset by holding the integral of the previous deviation (an integration operation) and a function of predicting future movement (a differential operation) are incorporated.
• In addition, the[0187]pneumatic circuit610 is controlled in the embodiment through the acceleration feedback control, implemented based upon outputs from pressure sensors (not shown) disposed at theports536 and538 of thepneumatic cylinder520 in order to control the external disturbance, as shown in FIG. 16, and the velocity feedback control implemented based upon the output of thelinear encoder505 taken into the means forcontrol700, as shown in FIG. 15.
• The positional control of the[0188]upper electrode420 may be achieved by setting the target position over a plurality of stages preceding the ultimate position to which theupper electrode420 is to be moved and by driving theupper electrode420 gradually. In this case, abrupt drive or abrupt vibration attributable to material properties such as the viscosity and the density of the air used to drive the pneumatic cylinder can be minimized. As a result, problems of attracting particles inside thechamber402 and the like while driving the upper electrode with a pneumatic cylinder do not occur.
• A structural example that may be adopted in the[0189]pneumatic circuit610 is now explained. FIG. 17 is a circuit diagram of a structure that may be adopted in thepneumatic circuit610. FIGS. 18 and 19 are functional diagrams illustrating the operation of thepneumatic circuit610. Thepneumatic circuit610 is in a neutral state in FIG. 17, is engaged in the drive control of theupper electrode420 in FIG. 18 and is in a state of emergency stop in FIG. 19.
• As shown in FIGS. 15 and 17, the[0190]pneumatic circuit610 includes a 5-portelectromagnetic valve630 constituting a switching valve capable of switching the flow path to a neutral state or a drive control state in response to a valve control signal provided by theCPU720. A 5-port switching valve640 is disposed in a pipeline extending from the 5-portelectromagnetic valve630 and communicating with theupper port536 of thepneumatic cylinder520, and a 5-port switching valve650 is disposed in the pipeline extending from the 5-portelectromagnetic valve630 and communicating with thelower port538 of thepneumatic cylinder520. These 5-port switching valves640 and650, each used as a drive stop valve when effecting an emergency stop of thepneumatic cylinder520, can be controlled with a 3-portelectromagnetic valve660.
• Now, the specific relationship with which the individual valves are connected with each other is explained. The[0191]pneumatic source605 is connected to a p-port of the 5-portelectromagnetic valve630, and an a-port of the 5-portelectromagnetic valve630 is connected to a p-port of the 5-port switching valve640. In addition, a b-port of the 5-portelectromagnetic valve630 is connected to a p-port of the 5-port switching valve650. A c-port and a d-port of the 5-portelectromagnetic valve630 are used as discharge ports.
• With the 5-port[0192]electromagnetic valve630, the flow path can be switched to an N state, an L state or an R state. A force applying member such as a spring is disposed on each side of the 5-portelectromagnetic valve630, and a force is applied to the 5-portelectromagnetic valve630 to set it in the N state unless power is supplied in response to a valve control signal provided by the means forcontrol700. Then, if positive power is supplied in response to the valve control signal, for instance, the 5-portelectromagnetic valve630 is set in the L state against the force applied by the force applying members, whereas if negative power is applied in response to the valve control signal, the 5-portelectromagnetic valve630 is set in the R state against the force applied by the force applying members. When the 5-portelectromagnetic valve630 is in the N state, each port at the 5-portelectromagnetic valve630 is in a cut-off state. When the 5-portelectromagnetic valve630 is in the L state, its p-port and a-port are connected with each other and its d-port and b-port are connected with each other, whereas when the 5-portelectromagnetic valve630 is in the R state, its p-port and b-port are connected with each other and its c-port and a-port are connected with each other.
• The[0193]upper port536 of thepneumatic cylinder520 is connected to an a-port of the 5-port switching valve640 whereas thelower port538 is connected to an a-port of the 5-port switching valve650. With both the 5-port switching valve640 and the 5-port switching valve650, the flow path can be switched to either the N state or the L state. At each of the 5-port switching valves640 and650, a force applying members such as a spring is provided on one side thereof to apply a force to the 5-port switching valve to set it in the N state unless compressed air is supplied through the 3-portelectromagnetic valve660. As compressed air is supplied through the 3-portelectromagnetic valve660, the 5-port switching valves enter the L state against the force applied by the force applying members. At each of the 5-port switching valves640 and650, the p-port and a b-port are connected with each other and a c-port and the a-port are connected with each other in the N state, and the p-port and the a-port are connected with each other and the d-port and the b-port are connected with each other in the L state.
• The[0194]pneumatic source605 is connected to a p-port of the 3-portelectromagnetic valve660, and a b-port and an a-port at the 3-portelectromagnetic valve660 are connected with each other. It is to be noted that the b-port at the 3-portelectromagnetic valve660 is used as a discharge port. As shown in FIG. 15, the flow path is switched to either the N state or the L state at the 3-portelectromagnetic valve660 based upon the drive enabled signal provided by theinterlock circuit760. A force applying member such as a spring is provided on one side of the 3-portelectromagnetic valve660 and a force is applied to set the 3-portelectromagnetic valve660 in the N state unless power is supplied in response to the drive enabled signal provided by the means forcontrol700. Then, as the drive enabled signal is output, it enters the L state against the force applied by the force applying member. At the 3-portelectromagnetic valve660, the p-port is cut off and the b-port and the a-port are connected with each other in the N state, whereas the p-port and the a-port are connected with each other and the b-port is cut off in the L state.
• When the[0195]switch620 of thepneumatic source605 is in an OFF state, as shown in FIG. 17, the output of the drive enabled signal from theinterlock circuit760 is stopped and thus, the flow path at the 3-portelectromagnetic valve660 is in the N state and the flow path at the 5-portelectromagnetic valve630, too, is in the N state in thepneumatic circuit610 adopting the structure described above. In this neutral state, theports536 and538 at thepneumatic cylinder520 are cut off from thepneumatic source605 by the 5-portelectromagnetic valve630, and, as a result, theupper electrode420 is held in a stopped state.
• As the[0196]switch620 of thepneumatic source605 is turned on, the drive enabled signal is output from theinterlock circuit760, thereby setting the flow path at the 3-portelectromagnetic valve660 in the L state. As a result, the flow path at the 5-port switching valves640 and650 each enter the L state. Consequently, drive of theupper electrode420 is enabled with the compressed air supplied to thepneumatic cylinder520 by switching the flow path at the 5-portelectromagnetic valve630.
• When the[0197]upper electrode420 is to move downward, for instance, from this state, the flow path at the 5-portelectromagnetic valve630 is set in the L state, as shown in FIG. 18. In response, the compressed air from thepneumatic source605 is guided in through theupper port536 at thepneumatic cylinder520 and is discharged through thelower port538, causing the slidingsupport member504 to move downward and ultimately causing theupper electrode420 to move downward.
• When the[0198]upper electrode420 is to move upward, for instance, from the neutral state shown in FIG. 17, the flow path at the 5-portelectromagnetic valve630 is set in the N state unlike in the operation shown in FIG. 18. As the stop signal from theinterlock circuit760 enters the OFF state, the flow path at the 3-portelectromagnetic valve660 is set in the L state under these circumstances as well. As a result, the flow paths at both the 5-port switching valve640 and the 5-port switching valve650 are set in the L state. In response, the compressed air from thepneumatic source605 is guided in through thelower port538 at thepneumatic cylinder520 and then discharged through theupper port536, causing the slidingsupport member504 to move upward and ultimately causing theupper electrode420 to move upward.
• FIG. 19 shows the state of the[0199]pneumatic circuit610 when an emergency stop is applied while driving the upper electrode. As the stop signal from theinterlock circuit760 is turned on, the flow path at the 3-portelectromagnetic valve660 enters the N state. As a result, the flow paths at the 5-port switching valves640 and650 both enter the N state. In response, the compressed air from thepneumatic source605 is guided through thelower port538 at thepneumatic cylinder520, and the compressed air from thepneumatic source605 is cut off from both theupper part536 and thelower port538 at thepneumatic cylinder520, thereby stopping the slidingsupport member504 and stopping theupper electrode420.
• FIGS. 20 and 21 present the results of tests conducted by implementing the specific control shown in FIG. 16 with the[0200]pneumatic circuit610 achieved in the embodiment as described above with the target position set over a plurality of stages preceding the ultimate position to which theupper electrode420 was to move. FIG. 20 is a graph of the relationship between the position of theupper electrode420 and the time observed by gradually driving theupper electrode420 upward, whereas FIG. 21 is a graph of the relationship between the position of theupper electrode420 and the time, observed by gradually driving theupper electrode420 downward. FIGS. 20 and 21 indicate that stable and accurate follow-up control was achieved to drive theupper electrode420 upward or downward to set the target position.
• Various indices measured based upon these test results, which include approximately ±0.15 mm representing the accuracy with which the upper electrode was stopped and approximately 60 mm/sec representing the operating speed, indicate that the structure adopted in the embodiment is highly viable in practical application. In other words, highly accurate positional control is enabled by employing the[0201]plasma processing apparatus400
• In the plasma processing apparatus in the embodiment described in detail above, the sliding[0202]support member504 is provided independently of thepneumatic cylinder520 to slidably support theupper electrode420 along one direction (e.g., the vertical direction), and thus, any load (external disturbance) that would be applied to thepneumatic cylinder520 along a direction other than the one direction is eliminated to allow thepneumatic cylinder520 to move only along the one direction. Consequently, the positional control for theupper electrode420 can be implemented with a high degree of accuracy with thepneumatic cylinder520.
• The[0203]rod502 at thepneumatic cylinder520 is disposed at an approximate center of theupper electrode420 to prevent decentering of the load applied to therod502 at thepneumatic cylinder520 and the occurrence of a moment and, as a result, the position of the electrode can be controlled with an even higher degree of accuracy.
• It is to be noted that while the[0204]upper electrode420 is driven by using thepneumatic cylinder520 in the embodiment described above, the lower electrode may instead be slidably supported and be driven with thepneumatic cylinder520. However, at the lower electrode on which the workpiece such as a wafer or a liquid crystal substrate is placed, various additional mechanisms including a workpiece holding mechanism, a workpiece back side gas mechanism and an electrode temperature adjustment mechanism must be mounted, whereas the upper electrode does not need such additional mechanisms. For this reason, a higher degree of positional control accuracy can be achieved for theupper electrode420 by driving theupper electrode420 with the pneumatic cylinder and thus minimizing the load applied to therod502 at thepneumatic cylinder520.
• In addition, the components such as the[0205]upper electrode420, the upperelectrode drive mechanism500 for theupper electrode420, thepneumatic circuit610 and the means forcontrol700 may be provided as an integrated upper electrode unit, as shown in FIG. 14, to facilitate positional control to be implemented with a pneumatic cylinder on anupper electrode420 in an existing plasma processing apparatus simply by installing the upper electrode unit.
• In conjunction with the plasma processing apparatus and the upper electrode unit described above, highly accurate positional control can be achieved with a pneumatic cylinder functioning as a pneumatic actuator by minimizing the load applied to the pneumatic cylinder.[0206]
• It is to be noted that while an explanation is given above in reference to the embodiment on an example in which the present invention is adopted in a plasma etching apparatus, the present invention may instead be adopted in a different type of processing apparatus such as a film forming apparatus or an ashing apparatus. In addition, while the workpiece processed in the embodiment described above is a semiconductor wafer, the present invention is not limited to this example, and the present invention may be adopted to process a workpiece such as a glass substrate for a flat display (FPD) in a liquid crystal display (LCD) device, i.e., an FPD substrate which may be an LCD substrate.[0207]

Claims (7)

What is claimed is:

1. A plasma processing apparatus that executes plasma processing on a workpiece placed inside a processing chamber by generating plasma with a processing gas supplied through a gas supply hole at a gas supply unit disposed within said processing chamber, wherein:

an interchangeable insert member that prevents entry of charged particles in the plasma generated inside said processing chamber into said gas supply unit is mounted at said gas supply hole in said gas supply unit.

2. A plasma processing apparatus according toclaim 1, wherein:

said insert member comprises a gas passage formed therein that communicates between an entry side and an exit side of said gas supply hole; and

said gas passage comprises a passage that regulates the flow along a central axis of said gas supply hole and extends perpendicular to or at an angle to the central axis.

3. A plasma processing apparatus according toclaim 1, wherein:

said insert member comprises a gas passage formed therein that communicates between an entry side and an exit side of said gas supply hole while regulating the flow along a central axis of said gas supply hole at all times.

4. A plasma processing apparatus according toclaim 3, wherein:

said gas passage is a spiral passage.

5. A plasma processing apparatus according toclaim 4, wherein:

a section of said gas passage has a shape with a thickness along the central axis of said gas supply hole set larger than a width thereof.

6. A plasma processing apparatus according toclaim 1, wherein:

insert members constituted of different materials are used in correspondence to different types of gas used in said plasma processing.

7. A plasma processing apparatus according toclaim 1, wherein:

insert members with gas passages formed in different shapes are used in correspondence to different density levels of the plasma generated inside said processing chamber.

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